Automatic control of a centrifuge



Oct. 20, 1970 c m L 3,535,158

AUTOMATI C CONTROL OF A CENTRIFUGE Filed Oct. 9, 1967 FAT CLARIFIED LIQUOR SUPPLY LIQUOR Thomas CZ/YcBrLde United States Patent O US. Cl. 127-24 7 Claims ABSTRACT OF THE DISCLOSURE An automatic control device for a continuous centrifuge comprises valve means on the light-phase discharge line of the centrifuge which open in response to a preset timer and close in response to an interface detection, e. g., a pressure change in the discharge line.

SPECIFICATION In general, the present invention relates to the automatic control of a centrifuge. In particular, it concerns means for regulating, on an intermittent flow basis, the discharge from a continuous centrifuge. More par ticularly, it involves an automatic control device for the light-phase discharge line of a continuous centrifuge.

In the operation of a continuous centrifuge, supply material is passed in a steady stream through a part of the centrifugal apparatus where it is subjected to cen trifugal force and continuously discharged from the ap paratus in the form of a light-phase discharge and a heavy-phase discharge. One such continuous centrifuge is a centrifugal clarifier. In such a clarifier, a stream of liquid is subjected to a centrifugal force to remove the solid or liquid contaminants. Such clarifier-s are used in a number of different applications.

One such application is in clarifying refinery liquors. For example, a De Laval Centrifugal Separator (Model GRPX-2l3) has been employed as a clarifier to remove the small (e.g., 0.5l.5%) amount of fat (and other light insolubles) from the neutralized supply liquor (feed) in a corn syrup refining process. In such a process the clarifier is operated so as to remove all the fat, thereby producing a clarified liquor. The light-phase discharge contains the fat (and light insolubles) and, usually, a small amount of the clarified liquor. The heavy-phase discharge is the product stream which comprises clarified liquor and no fat. Optimum performance minimizes the amount of clarified liquor loss in the light-phase discharge. However, due to the low concentration of fat in the supply liquor and due to the changes in concentration of fat in the supply liquor, problems result in controlling the clarifier so as to insure such optimum performance.

It is" an object of the present invention to provide means for automatically controlling the discharge from a centrifuge.

Another object of the present invention is to provide automatic control means for regulating, on an intermittent fiow basis, the light-phase discharge from a continuous centrifuge.

A further and more specific object of the present invention is to provide a means for minimizing the clarified liquor losses in the light-phase discharge from a continuous clarifier.

A still further object is to provide means for effectively controlling the separation of relatively small amounts of contaminants from liquid materials.

Other objects will be apparent from the disclosure, including the drawing, that follows.

It has now been discovered that the above objects and others may be achieved by means of the automatic discharge control device of the present invention. In general,

this device comprises interface sensing means, valve means, and a timer combined as described hereinafter.

The drawing is a schematic illustration of a device of the present invention controlling a continuous clarifier in a corn syrup refining process.

Interface sensing means are means which are capable of detecting the presence of an interface between two different liquids; for example, clarified liquor and fat-containing light-phase discharge. This interface occurs in the light-phase discharge line of a continuous centrifuge when product, i.e., heavy-phase discharge, e.g., clarified liquor, starts to pass through this line. At the interface, there is a change in some of the physical properties of the liquid passing through the light-phase discharge line. One of these properties is selected for sensing by the interface sensing means.

Suitable interface sensing means are known in the art and include pressure sensing means, viscosity sensing means, and thermal conductivity sensing means. Preferred interface sensing means are pressure sensing means. Suitable pressure sensing means are known in the art and, per se, form no part of the present invention. Such means are positioned in the light-phase discharge line of the centrifuge to be controlled. The pressure sensing means should be capable of detecting pressure differences in the range of about 0 p.s.i.g. to 10 p.s.i.g. within the lightphase discharge line.

The valve means employed in the apparatus of the present invention may be any conventional means for starting and stopping the flow of liquid through the lightphase discharge line. An electrically actuated valve is particularly suitable for use.

The timer employed in the apparatus of this invention is adapted to open the valve means in response to a preset time interval. One such suitable timer is Syracuse Electronics Corporation Model TER 30321.

The invention may be further described by reference to the following illustrative example.

EXAMPLE The light-phase discharge from a De Laval GRPX-213 Centrifugal Separator was automatically controlled according to the present invention. This centrifuge was in operation as a clarifier in a corn syrup refining process. The supply liquor to the centrifuge was an acid converted, neutralized hydrolyzate of about 22 Baum (Comm), and 42 DE. It contained about 1.3% fat (and other light insolubles). The desired operation was to remove all fat from the product, i.e., clarified liquor, stream; and to minimize the loss of clarified liquor in the light-phase discharge. The light-phase discharge line was provided with an electrically actuated on-oiT valve. The valve opened in response to an electric timer. The discharge line was further provided with pressure sensing means comprising a liquid filled volumetric pressure sensing system consisting of a Mansfield and Green Type SM diaphragm seal connected to a Foxboro pressure transmitter Model 15Al by means of /8" tubing. The pneumatic output signal from the transmitter actuates a pressure switch, e.g., Barksdale Model D2T-Hl8. The timer setting was arbitrarily selected to open the valve about 2 minutes after a previous closing of the valve. The valve stayed open until an interface was detected, as indicated by a pressure decrease in the line. In general, the valve remained open for about 20 seconds. Samples of the product stream and light-phase discharge stream were analyzed and/or observed. The analysis showed essentially no fat in the product stream. In addition, the liquor loss in the light-phase discharge was minimized.

It is apparent from the above example that the automatic control device of the present invention is eminently suitable for controlling the light-phase discharge of a continuous centrifuge on an intermittent basis. It should be understood, however, that the above example is for illustrative purposes only and not intended to limit the present invention in any respect.

Referring to the drawing, there is shown schematically the exemplified corn syrup refining process in which a continuous centrifuge is used as a clarifier and is controlled according to the present invention. During operation, supply liquor is continuously provided, e.g., by conventional supply means (not shown), to centrifuge 1 which is a hermetically sealed, disc-type apparatus. In centrifuge 1 a separation of the supply liquor into a product (clarified liquor) stream and a contaminant (fat) stream is effected. The product stream continuously discharges from centrifuge 1 through continuous discharge means 2. Light-phase discharge line 3 and accumulating means (not shown) within centrifuge 1 accumulate the separated contaminant, i.e., fat. Valve 4 regulates the flow of the fat stream. Valve 4 opens periodically in response to a preset timer 5. Valve 4 closes in response to a signal from interface sensing means 6. When valve 4 is closed, fat accumulates in a portion of centrifuge 1 and line 3. When valve 4 is open the accumulated fat discharges through line 7. Valve 4 remains open until sensing means 6 detects the presence of an interface between the fat and the clarified liquor, at which time valve 4 closes.

In addition to the interface sensing means, the valve means and the timer, the automatic control device is also preferably provided with a time delay. This time delay prevents, for a few seconds, the valve from closing, in order to give the light-phase discharge line between the valve and the interface sensing means time to fill.

The continuous centrifuges with which the automatic discharge control device of the present invention will have special utility are hermetically sealed, disc-type apparatus. A preferred centrifuge is the De Laval Centrifugal Clarifier Model GRPX213.

While the automatic discharge control device has been exemplified as controlling a clarifier employed in a corn syrup refining process, it is apparent that continuous centrifuges controlled by the device of the present invention have utility in many other processes.

While the invention has been described in connection with one specific embodiment thereof, it will be understood that it is capable of further modifications and this application is intended to cover any variations, uses, or adaptations of the invention, following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention per tains and as may be applied to the essential features hereinbefore set forth and as fall within the scope of the invention and the limits of the appended claims.

What is claimed is:

1. In combination with a continuous centrifuge, an automatic discharge control device, for regulating on an intermittent flow basis, the flow from a discharge line of said centrifuge comprising valve means positioned in said discharge line, interface sensing means operatively connected to said valve means and adapted to close said valve means in response to an interface detection in said discharge line and a timer adapted to open said valve in response to preset time interval.

2. A combination as defined by claim 1 wherein said valve means are electrically actuated.

3. A combination as defined by claim 1 wherein said interface sensing means comprise pressure sensing means.

4. A combination as defined by claim 1 wherein said interface sensing means comprise viscosity sensing means.

5. A combination as defined by claim 1 wherein said continuous centrifuge is a hermetically sealed, disc-type apparatus.

6. A process of automatically controlling, on an intermittent flow basis, the light-phase discharge from a continuous centrifuge which comprises sensing the lightphase discharge to detect an interface, stopping the lightphase discharge when said interface is detected, and periodically permitting the light-phase to discharge.

7. A process as defined by claim 6 wherein the continuous centrifuge is employed as a clarifier in a corn syrup refining process.

References Cited UNITED STATES PATENTS 2,113,809 4/1938 Lincoln 23319 2,628,023 2/1953 Dahlstedt 233-19 3,114,655 12/1963 Jiskra 12756 3,347,455 10/1967 Borden 23319 3,408,000 10/1968 Nilson 233-19 3,437,267 4/1969 Dahlbcrg 23321 FOREIGN PATENTS 105,479 9/ 1942 Sweden. 536,334 1/1957 Canada.

OTHER REFERENCES Smith: Applications I & EC 53:439, 40 (1961).

Alexander: Centrifuging of Mixed Juice in Sugar Industry. Abstracts, v. 20, Abs. 666 (1958).

Cremer et 211.: Chemical Engineering Practice v. 3, pp. 299-303, 310 (1957).

MORRIS O. WOLK, Primary Examiner D. G. CONLIN, Assistant Examiner US. Cl. X.R. 

